Integrated anti-lock braking and traction control system

ABSTRACT

An integrated anti-lock braking (ABS)/traction control (TC) braking system for a vehicle is provided including in a preferred embodiment a controller cognizant of the rotational condition of a vehicle wheel for signalling the system to an ABS or TC mode. A master cylinder delivers pressurized fluid to the wheel brake. An actuator frame with a bore is fluidly connected with the master cylinder and the wheel brake generally along a first end. A first fluid network connects the master cylinder with the wheel brake. A reservoir fluidly connected with the bore and the brake for selective receipt of fluid from the bore. A second fluid network connects the reservoir and the ends of the bore with one another and fluidly connects the reservoir with the wheel brake. A check valve preventing flow from the master cylinder to the brake via the first fluid network. A valve responsive to the controller isolates the reservoir from the second fluid network when the integration is in the normal operation or the TC mode. A valve responsive to the controller which prevents fluid communication through the second fluid network when the integration is in an ABS mode. A valve responsive to the controller which prevents fluid communication between the master cylinder and the bore when the integration is in a TC mode. A piston is slidably mounted in the bore with a head separating the first and second ends of the bore.

FIELD OF THE INVENTION

The field of the present invention is that of an integrated anti-lockbraking system (ABS) and traction control (TC) braking system for avehicle and methods of utilization thereof.

DISCLOSURE STATEMENT

Anti-lock braking systems typically modulate the pressure delivered to avehicle wheel brake to prevent the vehicle wheel from locking up in thebraking condition. Conversely, traction control systems typicallyincorporate an automated braking system which actuates a brake toprevent spinning of the vehicle wheel, thereby maximizing the tractionwhich can be exerted by that wheel. A more detailed analysis ofanti-lock braking systems can be found in commonly assigned U.S. Pat.Nos. 4,756,391 and 4,653,815. A more detailed explanation of tractioncontrol systems which utilize actuation of a vehicle wheel brake fortraction control can be found in commonly assigned U.S. Pat. application223,327 filed Jul. 8, 1988 now U.S. Pat. No. 4,976,500.

The present invention provides an ABS/TC integration which is analternative to that provided and described in coassigned U.S. Pat.Parker et al 4,938,543 and copending U.S. Pat. application Villec438,174 filed Nov. 16, 1989 now U.S. Pat. No. 5,051,434.

SUMMARY OF THE INVENTION

The present invention provides an ABS and TC integration apparatus andmethod of utilization thereof which allows a common actuator mechanismto provide the ABS and TC functions.

It is an object of the present invention to provide an integrated ABS/TCbraking system and method utilization thereof.

Other objects and advantages of the present invention can become moreapparent to those skilled in the art as the nature of the invention isbetter understood from the accompanying drawings and a detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view with portions illustrated schematically of apreferred embodiment ABS/TC integrated braking system according to thepresent invention;

FIG. 2 is a view similar to FIG. 1 of an alternative preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1 an integrated anti-lock (ABS)/traction control (TC)braking system 7 has a master cylinder 4 for delivering pressurizedfluid to a vehicle fluid actuated wheel brake 6 (commonly referred to asa brake cylinder for drum type brakes or as a caliper for disc typebrakes). The master cylinder is linked with a pedal linkage 12 which ismanipulated by a vehicle operator.

Between the master cylinder 4 and the wheel brake 6 is an actuator 8with a frame 10. The actuator frame 10 has a multidiametered bore 11that includes a large diameter actuator bore 14 with a first end 16 anda second end 18. Slidably and sealably mounted within the bore 14 of theactuator frame 10 is a piston 20 having a head section 22 and aconnected rod 24. The piston head 22 sealably separates the first end 16and second end 18 of the bore with an 0-ring type seal 26. The pistonrod 24 is also sealed within the bore 11 by an 0-ring type seal 28.

The master cylinder 4 is fluidly connected with the second end 18 of theactuator bore 14 via a check valve 30. The check valve 30 is positionedin such a manner that pressure from the master cylinder 4 automaticallycloses the check valve 30 and as illustrated is biased by a spring 32.Between the check valve and the master cylinder 4 is a normally opensolenoid valve 34 which provides the means of preventing fluid flow fromthe master cylinder 4 to the wheel brake 6 via a first fluid network 40which includes a line 42 which runs from the master cylinder 4 to thecheck valve 30; the bottom of the enlarged diameter portion of thesecond end 18 of the actuator bore 14, and fluid lines 44 and 46 whichfluidly connect the actuator bore 14 with the wheel brake 6.

The actuator bore first end 16 via a second fluid network 50 is fluidlyconnected with a reservoir 52 through a normally closed solenoid valve54. The second fluid network 50, which is inclusive of lines 62, 64, 44and 46 also connects the reservoir 52 with the wheel brake 6. The secondfluid network 50 also provides a parallel path joining the first end 16of the actuator bore 14 with the second end 18 of the actuator bore 14.The normally closed solenoid valve 54 provides for selective isolationof the reservoir 52 from the actuator bore 14 or the wheel brake 6. Alsoprovided in the second fluid network 50 is a normally open solenoidvalve 66 in a portion of the second fluid network 50 providing parallelconnection of the first and second ends 16, 18 respectively of theactuator bore 14.

Alternatively (not shown) the reservoir 52 and the second fluid network50 can fluidly connect the reservoir with the top of the actuator bore14 via a solenoid valve. Fluid line 62 could then fluidly connect thebore 14 with a portion of the fluid line 64 before the solenoid valve 66and opposite the connection of line 46.

The rod 24 of the piston 20 is operatively associated and contactingwith a non-rotative nut 70 which is threadably engaged and penetrated bya drive screw 72 (commonly referred to as a ball screw). The drive screw72 is gearably engaged with an electric motor 80, via gear train 84. Themotor 80 is responsive to signals given by a system controller 82. Thecontroller 82 is cognizant of the rotational condition of the wheel 9via a sensor 13. When the wheel 9 is at a predetermined rotationalcondition the controller 82 will give a signal to place the brakingsystem 7 into an ABS or a TC mode. The motor 80, solenoid valves 34, 66and 54 are responsive to signals given by the controller and theiroperations will be governed by the controller 82.

When in normal operation the piston head 22 will be adjacent to thesecond end 18 of the actuator bore 14 and will contact a stem 33 of thecheck valve 30 thereby retaining the check valve 30 in an open position.Because of the area differential of the piston 20 at its sealed portionsalong seals 26 and 28, equal pressure on both sides of the piston head22 will bias the piston 20 to the retracted position as shown in FIG. 1.

The underside of the head of the piston head 22 is grooved or chamfered,or there may be grooves within the portion of the actuator frame borewhich interferes with the piston head 22 so that a fluid communicationis provided from the master cylinder 4 through the normally opensolenoid valve 34, pass the check valve 30 and out to the brake via theline 44. As illustrated, the piston head 22 has an annular groove 23which provides for fluid communication.

In normal operation the check valve 30 will normally be held in a secondopen position versus a first closed position, and the valve 54 will beclosed isolating the reservoir 52 from both the wheel brake 6 and thefirst end 16 of the actuator bore 14.

Referring to FIG. 1 if a skidding condition is sensed the controller 82will signal the braking system 7 to an ABS relief cycle. The solenoidvalve 34 will remain in a normally open condition. Solenoid valve 66will be signalled to a closed position and the normally closed solenoidvalve 54 connecting the first end 16 of the actuator bore 14 with thereservoir 52 will then be opened. The motor 80 will be signalled topower a gear train 84 and drive screw 72 to extend the piston 20 withinthe actuator bore 14. Any fluid on top of the piston head will be pushedinto the reservoir 52. Since the wheel brake 6 is now exposed to thevolume underneath the piston head 22, extension of the piston 20 upwardwill cause an increase in the volume that the fluid within the wheelbrake 6 is exposed to therefore causing the pressure within the wheelbrake 6 to be reduced.

On a pressure reapply the motor 80 will be signalled to reverse forcingthe piston 20 downward to a pressure reapply. If by chance there is aneed for pressure augmentation (due to the ABS mode being initiallyactuated when the wheel 9 is on ice and thereafter the wheel 9 is now onfirmer pavement allowing greater brake pressure to be applied) thepiston head 22 will come down fully hitting the stem 33 of the checkvalve 30 therefore allowing additional fluid from the master cylinder 4to be delivered to the wheel brake 9. One advantage of the presentinvention is that pressure augmentation occurs automatically andmechanically without the requirement of electrical signalling or aninput from a controller or pressure sensor which senses the need forsuch a response.

If the controller 82 is aware that TC situation has occurred, thesolenoid valve 34 will be signalled to the closed position isolating themaster 4 cylinder from the wheel brake 6. Solenoid valve 54 will bemaintained in the closed position isolating the reservoir 52 from eitherthe first end 16 of the actuator bore 14 or the wheel brake 6. Thesolenoid valve 66 will be in the normal open position. Thereforeextension of the piston upward (by the motor 80) will cause an increasepressure in a wheel brake 6 since the fluid will be forced away from thefirst end 16 of the actuator bore 14 into the second end 18 (via thesecond fluid path) of the actuator bore 14 and the wheel brake 6. Thepiston rod 24 provides volumetric differential between the first 18 andsecond 16 ends of the actuator bore 11. Thereby extension of the pistonupward causes increased pressure in the fluid exposed to the wheel brake6. On a pressure release cycle of TC the motor 80 will be signalled toreverse (retract) the piston allowing the volume of the system exposedto the wheel brake 6 to be increased and therefore reduce the pressure.

FIG. 2 shows an alternative preferred embodiment 15 of the presentinvention with item performing similar function being given the samereference number wherein the functions of the prior solenoid valves 54and 66 solenoid valves have been combined into a single three-waysolenoid valve 75 which in the normal braking condition isolates thereservoir 52 from either the first end 16 of the actuator bore 14 or thewheel brake 6. The first end 16 and second end 18 of the bore arefluidly connected. In the ABS mode solenoid valve 75 isolates thereservoir 52 from the wheel brake 6 while exposing the reservoir to thefirst end 16 of the bore 14. In the TC mode, the solenoid valve 75functions the same as during the normal braking operation.

Several advantages that both embodiments of the present inventionprovide are a high TC pressure versus the size of the motor ratio, arelatively short piston stroke and actuator frame length. Also there isno requirement for a neutral position sensor to determine the positionof the piston or for a motor locking device which will preventbackdriving of the piston during normal brake application. Additionally,there are very few dynamic seals.

While a few of the embodiments of the present invention have beenexplained it will be really apparent to those skilled in the art of thevarious modifications which can be made to the present invention withoutdeparting from the spirit and scope of this application as it isencompassed by the following claims.

What is claimed:
 1. A braking system for a vehicle having anti-lockbraking capabilities and traction control braking capabilities for avehicle having a fluid actuated brake for a wheel comprising:a systemcontroller aware of the rotational condition of the wheel for signalingthe system to an anti-lock braking mode and to a traction control modefrom a normal mode of operation and from another mode of operationdiffering from the signaled mode of operation; master cylinder means fordelivering pressurized fluid to the wheel brake; an actuator frame witha bore having two ends, the bore being fluidly connected with the mastercylinder means and the wheel brake generally along the first end; afirst fluid network fluidly connecting the master cylinder means withthe wheel brake; a reservoir fluidly connected with the bore and thebrake for selective receipt of fluid from the bore; a second fluidnetwork fluidly connecting the reservoir and the two ends of the borewith one another and fluidly connecting the reservoir with the wheelbrake; check valve means having a first position preventing flow fromthe master cylinder to the brake via the first fluid network and thecheck valve means having a second position allowing flow from the mastercylinder to the brake via the first fluid network; means responsive tothe controller for isolating the reservoir from the second fluid networkwhen the braking system is in the normal mode of operation and when thebraking system integration is in traction control mode of operation;means responsive to the controller for preventing fluid communicationthrough the second fluid network between the two ends of the bore whenthe integration is in an anti-lock braking mode; means responsive to thecontroller for preventing fluid communication between the mastercylinder in the bore when the integration is in a traction control mode;a piston slidably mounted in the bore with a head sealably separatingthe first and second ends of the bore, the piston having a connected rodsealed with respect to the bore; mechanical means for retaining thecheck valve means to an open position when the piston head is adjacentto the first end of the bore during normal operation; and means toreversibly move the piston in response to the controller causing thepiston to open the check valve in normal operation.
 2. A braking systemas described in claim 1 wherein said means to reversibly move the pistonincludes an electric motor gearably engaged with a rotative drive screwhaving a non-rotative nut contacting with the rod of the piston.
 3. Abraking system as described in claim 1 wherein the means for isolatingthe reservoir from the second fluid network and for preventing fluidcommunication through the second network are embodied in a three-wayvalve.
 4. A braking system for a vehicle having anti-lock brakingcapabilities and traction control braking capabilities for a vehiclehaving a fluid actuated brake for a wheel comprising:a system controlleraware of the condition of the wheel for signaling the system to theanti-lock braking and the traction control mode from the regular modeand from a prior mode differing from the signaled mode; a mastercylinder for delivering pressurized fluid to the wheel brake; anactuator frame with a bore being fluidly connected with the mastercylinder along one end of the bore and with the wheel brake at generallythe same end of the bore; a first fluid network fluidly connecting themaster cylinder with the wheel brake; a reservoir fluidly connected withthe bore for selective receipt of fluid from the bore at an end of thebore opposite with the bore's connection with the master cylinder; asecond fluid network fluidly connecting the reservoir and the two endsof the bore, and the second fluid path also connecting the reservoirwith the wheel brake; a check valve having a first position preventingflow from the master cylinder to the wheel brake via the first fluidnetwork and a second position allowing flow; a three-way valveresponsive to the controller, the valve in the normal mode isolating thereservoir from the wheel brake and the bore and connecting the secondend of the bore with the wheel brake during normal operation, the valvehaving a second mode of operating during the anti-lock braking modewherein it connects the second end of the bore with the reservoir andisolates the reservoir from the wheel brake and wherein a third mode ofoperation the valve connects the second end of the actuator bore withthe wheel brake while isolating the reservoir from the bore or the wheelbrake; a solenoid valve responsive to the controller for preventingfluid communication between the master cylinder and the first end of thebore when the integration is in a traction control mode; a pistonslidably mounted within the bore with a head sealably separating thefirst and second ends of the bore the piston also having a connected rodsealed within the bore and the piston head being operatively associatedwith the check valve wherein the check valve is held in the secondposition when the piston is adjacent the first end of the bore allowingfor normal operation wherein fluid from the master cylinder flowsthrough the check valve and to the wheel brake via the cylinder; anon-rotative nut operatively associated with the piston rod; a drivescrew threadably engaged with the nut and the drive screw being gearablyconnected with a reversible motor responsive to signals by thecontroller to move the piston reversibly in response to the controller.